Update index.html to add logo

@n-brock create containers and foundation for future logo and other brand markings.

- [ ] create base structure for logo and main navigation/profile bar
- [ ] position structure towards top to resemble lo-fi wireframes
- [ ] ensure svg and basic menu items can be added without breaking other elements in game

Start in index.html and inspect the existing game layout and elements before adding the logo and navigation/profile structure. Use the referenced lo-fi wireframes as the visual target; done means the structure sits near the top, supports SVG and basic menu items, and does not break the game.

Vom Indexierungsmodell aus dem Issue-Text verfasst.